Concetta De Stefano

Università degli Studi di Messina | UNIME · Dipartimento di Scienze Chimiche

Defining the distribution of the chemical species in a multicomponent system is a task of great importance with applications in many fields. To clarify the identity and the abundance of the species that can be formed by the interaction of the components of a solution, it is fundamental to know the formation constants of those species. The determina...

A new, open-source, practical, modern and multi-platform Python application for concentrations calculation (PyES - Python Equilibrium Species) was developed by re-writing and implementing the ES4, a freeware computer program originally written using the BASIC programming language. Currently PyES has two working modes, i.e., titration simulation and...

The speciation of epinephrine (Eph ⁻) in the presence of alginate (Alg ²⁻) and two biological and environmental relevant metal cations (Cu²⁺, UO2 ²⁺) was investigated at T = 298.15K, I = 0.15–1.00 mol dm⁻³ in NaCl(aq). The formation of binary and ternary complexes was evaluated and, since epinephrine can behave as a zwitterion, the Eph ⁻/Alg ²⁻ int...

Purpose Indole-3-acetic acid is a protein-bound indolic uremic toxin deriving from tryptophan metabolism. Increased levels are associated with higher thrombotic risk and both cardiovascular and all-cause mortality. An emerging biomarker of cardiovascular disease is the monocyte-to-high-density lipoprotein ratio (MHR). The main purpose of this study...

The chelating and sequestering ability of a glyphosate metabolite, the aminomethylphosphonic acid (AMPA) towards bi- and trivalent metal cations, such as Ca²⁺, Mg²⁺, Zn²⁺, Cu²⁺ and Al³⁺, were investigated in aqueous solutions of NaCl, in an ionic strength range of 0.1 ≤ I/mol dm⁻³ ≤ 1.0 and at constant temperature of T = 298.15 ± 0.15 K. The invest...

Caffeic acid (CFA) is one of the various natural antioxidants and chemoprotective agents occurring in the human diet. In addition, its metal complexes play fundamental roles in biological systems. Nevertheless, research on the properties of CFA with lanthanide metals is very scarce, and little to no chemical or biological information is known about...

The interactions of dopamine [2-(3,4-Dihydroxyphenyl)ethylamine, (Dop−)] with cadmium(II), copper(II) and uranyl(VI) were studied in NaCl(aq) at different ionic strengths (0 ≤ I/mol dm−3 ≤ 1.0) and temperatures (288.15 ≤ T/K ≤ 318.15). From the elaboration of the experimental data, it was found that the speciation models are featured by species of...

The binding ability of five bifunctional 3-hydroxy-4-pyridinones towards Cu2+ and Fe3+ was studied by means of potentiometric and UV–Vis spectrophotometric measurements carried out at I = 0.15 mol L−1 in NaCl(aq),T = 298.15 K and 310.15 K. The data treatments allowed us to determine speciation schemes featured by metal-ligand species with different...

The thermodynamics of the interaction of L-glutamic-N,N-diacetic acid (GLDA) with protons was studied potentiometrically at different temperatures, ionic strengths and ionic media. Four protonation constants and corresponding enthalpy changes occurred at infinite dilution together with temperature and ionic strength coefficients. The medium effect...

This work is focused on the design and preparation of polymer inclusion membranes (PIMs) for potential applications for stannous cation sequestration from water. For this purpose, the membranes have been synthesized employing two polymeric matrices, namely, polyvinylchloride (PVC) and cellulose triacetate (CTA), properly enriched with different pla...

In this paper, potentiometry and calorimetry were used to determine the thermodynamics of interaction between risedronate and four bivalent metal cations, namely: Mg²⁺, Zn²⁺, Pb²⁺, and Cu²⁺ in aqueous NaCl solutions at different ionic strengths and at T = 298.15 K. The data analysis allowed us to ascertain that the main species formed were the MLH2...

Background and Aims Indole-3-acetic acid (IAA, also called auxin) is a protein-bound indolic uremic toxin deriving from tryptophan metabolism by the intestinal bacteria. Previous studies have shown that increased IAA is associated with enhanced tissue factor synthesis in endothelial and peripheral blood mononuclear cells, oxidative stress and endot...

Background: Metabolic and physicochemical evaluation is recommended to manage the condition of patients with nephrolithiasis. The estimation of the saturation state (β values) is often included in the diagnostic work-up, and it is preferably performed through calculations. The free concentrations of constituent ions are estimated by considering the...

The development of sustainable and safe strategies to protect the environment and human health from the harmful effect of metals has become an issue of great concern for the scientific community. Aluminium is abundant in nature but with low bioavailability, under normal environmental conditions. However, acid rains and the extensive employment of t...

The current work investigates the protonation constants of gabapentin (GP), 2-[1-(aminomethyl)cyclohexyl]acetic acid and the stability constants for the binding of GP to Ca2+ and Mg2+ in a wide range of temperature and ionic strength conditions [283.15 ≤ T/K ≤ 318.15 and ionic strengths of NaCl(aq), 0.12 ≤ I/mol·dm−3 ≤ 4.84]. The pH-potentiometric...

8-hydroxyquinoline-2-carboxylic acid (8-HQA) has been found in high concentrations (0.5–5.0 mmol·dm−3) in the gut of Noctuid larvae (and in a few other lepidopterans), in which it is proposed to act as a siderophore. Since it is known that many natural siderophores are also involved in the uptake and metabolism of other essential elements than iron...

Kynurenine pathway of tryptophan metabolism is involved in the pathophysiology of chronic kidney disease (CKD) and diabetes mellitus, mainly through the inflammation-induced activity of indoleamine 2,3-dioxygenase (IDO), and few studies have investigated its potential link with proteinuria. Renin–angiotensin system inhibitors (RASis) are recommende...

Background and Aims Kynurenine pathway of tryptophan metabolism is involved in the pathophysiology of chronic kidney disease (CKD) and diabetes mellitus (DM), mainly through the inflammation-induced activity of indoleamine 2,3-dioxygenase (IDO). Renin-angiotensin-aldosterone system inhibitors (RAASis) [angiotensin converting enzyme inhibitors (ACEi...

The aim of this paper is to enhance the knowledge on the behaviour and thermodynamic properties of natural and synthetic biopolymers in aqueous solutions. The acid-base properties of Carrageenan (Car), Xanthan gum (XG), Hydroxyethyl cellulose (HEC), Carboxymethyl cellulose (CMC), Acusol 445TM (Sol), Monopropylene glycol (MPG) and Polyethylene glyco...

The acid–base properties and complexing ability of some biologically relevant polyalcohols (erythritol, sorbitol, maltol, and ethylmaltol) toward bivalent metal cations have been determined by potentiometric measurements with an ISE-H⁺ glass electrode in NaNO3 aqueous solutions at I = 0.151 mol·kg–1 and T = 298.15 K. For the erythritol system, the...

Protonation of nicotinic acid has been investigated by means of potentiometric titrations at different temperatures 283.15 ≤ T (K) ≤ 383.15 and ionic strengths of NaCl(aq), 0.12 ≤ I (mol·kg⁻¹) ≤ 4.84 and mixed NaCl with MgCl2 or CaCl2. Stability constants of the CaL⁺ and MgL⁺ species were obtained by means of the ΔpK method. Different models (e.g....

The acid–base properties of two bifunctional 3-hydroxy-4-pyridinone ligands and their chelating capacity towards Zn2+, an essential bio-metal cation, were investigated in NaCl aqueous solutions by potentiometric, UV-Vis spectrophotometric, and 1H NMR spectroscopic titrations, carried out at 0.15 ≤ I/mol −1 ≤ 1.00 and 288.15 ≤ T/K ≤ 310.15. A study...

The experimental determination of water solubility (log S ⁰ ) and Setschenow coefficient (k m ) of a compound is a time-consuming activity, which often needs large amounts of expensive substances. This work aims at establishing two “open-source” chemometric models based on a regression tree that is able to predict the two abovementioned quantities....

A new polyaminocarboxylic bis-(3-hydroxy-4-pyridinone), derivative of DTPA, DTPA(PrHP) 2 , was synthesized starting from maltol by means of a coupling reaction of a protected 3-hydroxy-4-pyridinone and DTPA bis-anhydride. The DTPA(PrHP) 2 acid-base behavior was investigated by UV–Vis spectrophotometry and spectrofluorimetry at I = 0.15 mol L ⁻¹ in...

The interaction of the biodegradable ligand, l-glutamic acid N,N-diacetic acid tetrasodium salt (GLDA) with molybdenum(VI) was studied by determining stability constants at pH 6.00, T = 298.15 K, and ionic strength 0.0992 < I/mol·dm⁻³ < 2.5689 of sodium chloride. The ionic strength dependence of the stability constants was fitted to both extended D...

The acid-base properties and solubilities of 1,2,3-, 1,3,5-, 1,2,4-benzenetricarboxylic and 1,2,4,5-benzenetetracarboxylic acids at T = (298.15 ± 0.15) K in NaClaq, (CH3)4NClaq and in Synthetic Sea Water are reported. In synthetic sea water, the data were analyzed by means of the single salt approximation (BA). For each ligand, the total solubility...

The interaction of polyaspartic acid 2 kDa (PASP) biopolymer with the major cationic constituent of natural fluids (H⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺) were studied by ISE-H⁺ titrations. The acid-base properties of PASP were determined in different ionic media [NaNO3, NaCl, KCl, (CH3)4NCl and (C2H5)4NI] at different temperatures and ionic strengths. The data...

A new bis-(3-hydroxy-4-pyridinone) ligand (NTA(PrHP)2), derived from nitrilotriacetic acid (NTA), was synthesized and evaluated for its selective solution metal complexation capacity as well as its in vivo sequestering power for hard metal cations. After the study of its acid-base properties and determination of the protonation constants, the bindi...

Metal pollution, coming from both natural and anthropogenic sources, has become one of the most serious environmental problems. Various strategies have been tested with the aim of removing heavy metals from environment. In this contribution, containing a robust experimental work together with a critical literature analysis, the sequestering ability...

This paper reports the results on the study of a set of synthesized bifunctional 3-hydroxy-4-pyridinones chelators as potential aluminium sequestering agents. They were N-functionalized with alkyl-amino, -carboxylic and -(amino-carboxylic) groups, envisaging the improvement of the Al3+ sequestering capacity, in comparison with the marketed chelatin...

Solution thermodynamics of three aminophosphonic acids are studied in this work. In particular, the protonation constants [ log(KiH/mol kg⁻¹)] of N-phosphonomethyliminodiacetic acid (NTAP), N,N-Bis(phosphonomethyl)glycine (NTAP2) and Nitrilotris(methylenephosphonic acid) (NTAP3) and the solubility of NTAP were determined by potentiometric measureme...

The sequestration of Al³⁺ by etidronic acid (1‑Hydroxyethane‑1,1‑diyil)bis(phosphonic acid) (HEDPA), nitrilotriacetic acid and its phosphonic derivatives, namely N‑(phosphonomethyl)iminodiacetic acid (PMIDA, NTAP), N,N‑bis‑(phosphonomethyl)glycine (NTA2P) and [bis(phosphonomethyl)amino]methylphosphonic acid (NTA3P) was studied in aqueous solution a...

A potentiometric method has been used for the determination of the protonation constants of N-(2-hydroxyethyl)iminodiacetic acid (HEIDA or L) at various temperatures 283.15 ≤ T/K ≤ 383.15 and different ionic strengths of NaCl(aq), 0.12 ≤ I/mol·kg⁻¹ ≤ 4.84. Ionic strength dependence parameters were calculated using a Debye–Hückel type equation, Spec...

The complex formation between molybdate(VI) (MoO42-) and phytate [Phy, 1,2,3,4,5,6-hexakis(dihydrogen phosphate) myo-inositol] has been investigated at T = 298.15 K in NaCl(aq) at different ionic strengths (0 < I / mol dm-3 ≤ 1.0). In these experimental conditions, eight (MoO4)(Phy)Hr protonated species are formed, with 2 ≤ r ≤ 9. The corresponding...

Potentiometric measurements were carried out to study the protonation constants of risedronic acid (RA) in NaCl(aq), (CH3)4NCl(aq) and (C2H5)4NI(aq) at different ionic strengths and temperatures (283.15 ≤ T/K ≤ 318.15). In the same conditions, solubility measurements were also performed. Calorimetric measurements were done in NaCl to determine the...

The complex formation between a series of biologically, environmentally, and technologically relevant cations (namely Sn²⁺, Zn²⁺, Cu²⁺, Fe²⁺, Fe³⁺ and Al³⁺) and Diethylenetriamine-N,N,N′,N″,N″-Pentakis-(Methylenephosphonic) Acid (DTPMPA) has been investigated in NaCl aqueous solutions at I = 0.1 and I = 0.3 mol dm⁻³ and T = 298.15 K. The ligand use...

A potentiometric study on the acid–base properties and formation of complexes with alkali metals (i.e., Na⁺ and K⁺) of some poly(methyl vinyl ether-co-maleic) acids, namely, Gantrez AN169 (2000 kDa), S95 (220 kDa), and S97 (1200 kDa), was carried out under different experimental conditions consisting of the ionic medium, ionic strength, and tempera...

Thermodynamic information about the metal-ligand interaction between Fe³⁺, Zn²⁺, Cu²⁺ and Sn²⁺, and a biodegradable ligand as MGDA is reported. The speciation scheme was obtained by means of potentiometric measurements and isothermal titration calorimetry (to determine enthalpy changes) in NaCl medium. The formation of the ML and MLOH species was e...

In this paper, the sequestering ability of amoxicillin and ampicillin toward Mg²⁺ in NaCl aqueous solutions at different ionic strengths I = (0 to 1.0) mol·kg⁻¹ and temperatures of T = (288.15 to 318.15) K was investigated by potentiometry (ISE-H⁺, glass electrode). The complex formation constants determined at different ionic strengths and tempera...

The interaction of Zn(II) with ampicillin [(2S,5R,6R)-6-([(2R)-2-amino-2-phenylacetyl]amino)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2- carboxylic acid] and amoxicillin [(2S,5R,6R)-6-{[(2R)-2-amino-2-(4-hydroxyphenyl)-acetyl]amino}-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-24-carboxylic acid] in NaCl aqueous solution at diff...

This paper reports the results of a study on the determination of the protonation constants of MoO42 −, in NaClaq, NaNO3aq, KClaq, at different ionic strengths (0 < I/mol dm− 3 ≤ 5.0 in NaClaq, 0 < I/mol dm− 3 ≤ 3.0 in NaNO3aq and KClaq) and temperatures (278.15 ≤ T/K ≤ 318.15 in NaClaq, only 298.15 K in NaNO3aq and KClaq), by potentiometric (ISE-H...

This work is focused on the determination of the thermodynamic parameters of interaction between a biodegradable complexone, as MGDA (methylglycinediacetic acid), towards the major constituents of natural fluids, such as H⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺. The determination of their thermodynamic parameters of interaction was performed by potentiometric an...

This paper reports the results of the investigations carried out in synthetic sea water at different salinities for different classes of polycarboxylic acids. The investigations can be summarized as follows: (a) Determination of the protonation constants in such multicomponent solution in a salinity range 15 ≤ S ≤ 45, at t = 25 °C, for the linear d...

In this paper, new potentiometric, calorimetric, and voltammetric measurements are reported to model the behavior of d-gluconic acid in aqueous NaCl(aq) and NaNO3(aq) ionic media at different ionic strengths and temperatures (283.15 ≤ T/K ≤ 318.15) also in the presence of Sn2+ and Zn2+. The protonation constants of d-gluconic acid (Gluc- in its dep...

The protonation constants (log K-i(H)) in of L-glutamic acid N,N-diacetic acid tetrasodium salt (GLDA) were determined at T = 298.15 K and various ionic strengths in NaCl(aq), 0.18 <= I <= 3.20 mol.kg(-1), (CH3)(4)NCl(aq) 0.17 <= I <= 4.00 mol.kg(-1), and (C2H5)(4)NI(aq) 0.13 <= I <= 1.10 mol.kg(-1) by using the potentiometric method. The calculati...

Ethylenediamine-N,N'-disuccinic acid is a biodegradable alternative to EDTA, therefore its use for the sequestration of Ca(2+), Sn(2+), Cu(2+), Zn(2+) and Fe(3+) is analyzed. New data on its binding ability towards these cations were obtained with potentiometric, voltammetric and calorimetric measurements at different ionic strengths and at T = 298...

Alkali metal ions play very important roles in all biological systems, some of them are essential for life. Their concentration depends on several physiological factors and is very variable. For example, sodium concentrations in human fluids vary from quite low (e.g., 8.2 mmol dm−3 in mature maternal milk) to high values (0.14 mol dm−3 in blood pla...

The complex formation between Hg2+, CH3Hg+, Sn2+ and (CH3)2Sn2+ with some phosphonic derivatives of nitrilotriacetic acid (NTA), namely N-(phosphonomethyl)iminodiacetic acid (PMIDA, NTAP), N,N-bis(phosphonomethyl)glycine (NTA2P) and [bis(phosphonomethyl)amino]methylphosphonic acid (NTA3P), has been studied using potentiometry in NaCl aqueous soluti...

The formation of mixed hydrolytic species obtained by the interaction of dimethyltin(IV) {(CH3)2Sn2+ or DMT or M22+} with the monomethyltin(IV) (CH3Sn3+ or MMT or M13+) and trimethyltin(IV) {(CH3)3Sn+ or TMT or M3+} cations was studied in aqueous solutions of NaNO3, at I = 1.00 ± 0.05 mol·dm-3 and T = (298.15 ± 0.1) K, by the potentiometric techniq...

Solubility and acid-base properties of adrenaline were studied in NaCl aqueous solutions at different ionic strengths (0 <I/mol L(-1) < 3.0) and temperatures (T = 298.15 and 310.15 K), by means of different techniques: potentiometry, UV-spectrophotometry and spectrofluorimetry. The intrinsic solubility of the ligand was calculated from simple mass...

This paper reports the results of an investigation carried out on the interaction between Zn(II) and some hydroxocarboxylic ligands (L), namely: malate (Mala²⁻), tartrate (Tar²⁻) and citrate (Cit³⁻). The stability constants of the mono- and polynuclear ZniHjLk(2i+j−kz) species were determined by potentiometric measurements at T = 298.15 K in differ...

A model of synthetic saliva (SALMO, SALiva MOdel) is proposed for its use as standard medium in in vitro equilibrium and speciation studies of real saliva. The concentrations come out from the literature analysis of the composition of both real saliva and synthetic saliva. The chief interactions of main inorganic components of saliva, as well as ur...

This contribution reports the results of an investigation on the speciation of various lanthanoid(III) cations (Ln(3+)), namely, La3+ , Nd3+ , Sm3+ , Eu3+, Gd3+, Dy3+, and Yb3+, in the presence of reduced glutathione (or simply glutathione, GSH), in NaCl(aq) at I = 0.15 mol center dot dm(-3) and T = 298.15 K. GSH forms in all cases the same four sp...

In this paper new potentiometric titrations were performed on the protonation of phytate at different temperatures 278.15 K ≤ T/K ≤ 323.15, ionic strengths and in different ionic media, namely (CH3)4NCl (0.1 ≤ I/mol dm−3 ≤ 3.0) and (C2H5)4NI (0.1 ≤ I/mol dm−3 ≤ 1.2). A complete set of phytate protonation constants, with general formula HiPhy (with...

The solubility and the acid base properties of risedronic acid (RA) were studied in NaCl and (C2H5)4NI aqueous solutions at different ionic strengths and at T = 298.15 ± 0.1 K. The solubility of RA in the two salts is very different; in fact in NaCl(aq) the total solubility increases with increasing salt concentration up to mNaCl ≈ 2 mol·kg–1. For...

The acid-base and the UV behavior of 3-(3,4-dihydroxyphenyl)-propenoic acid (caffeic acid) was studied by potentiometry and UV spectrophotometry at T = 298.15 K and 0.1 <= I/mol L-1 in NaCl aqueous solution. The complex formation with Zn2+, Cu2+, Cd2+, (CH3)(2)Sn2+ at I = 0.1 mol L-1 in NaCl has been also determined by using potentiometric and spec...

This article describes the characterization of Polycyclic Aromatic Hydrocarbons (PAHs) in sediments of Milazzo Gulf (Italy) located in front of an oil refinery and a power plant. The investigated area is characterized by urban and industrial activities. The sixteen PAHs identified by the USEPA, as requiring priority monitoring, and other non USEPA...

Both mercury(II) and monomethyl mercury(II) poisonings are of great concern for several reasons. As it happens for other metals, chelation therapy is the most indicated treatment for poisoned patients. The efficacy of the therapy and the reduction of side-effects can be sensibly enhanced by an accurate knowledge of all the physiological mechanisms...

Diethylenetriamine-N,N,N′,N″,N″-pentakis(methylenephosphonic acid) (DTPMPA) is used in a wide range of industrial applications, mainly because of its binding ability toward several metal cations. Because of difficulties in its synthesis and purification, very little reliable data have been reported in the literature about the coordination chemistry...

The binding capacity of three aminopolycarboxylates [nitrilotriacetic acid (NTA), ethylene-glycol-bis(2-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), and diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid (DTPA)] and two aminopolyphosphonates {(1-hydroxyethane-1,1-diyl)bis(phosphonic acid) (HEDP) and [[(phosphonomethyl)imino]bis[2,1-ethanediyl...

The acid–base behavior of pyridine (py) was studied at different temperatures and ionic strengths in LiCl, NaCl, KCl, RbCl, CsCl, NaNO3, (CH3)4NCl, (C2H5)4NI, MgCl2, and CaCl2 aqueous solutions. The study was developed by means of potentiometric titrations with a ISE-H+ electrode and by the reanalysis of literature data. It was found that the proto...

The 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim]BF4, is an ionic liquid when pure. The acid base properties of aqueous solutions of [bmim]BF4 were examined by potentiometric titration. Then, protonation constants of glycine in binary mixtures of water and [bmim]BF4 were determined, from potentiometric titration data obtained at T = 298.2 K...

In this paper new solubility and potentiometric measurements are reported to model the behaviour of melamine in aqueous NaCl and (CH3)(4)NCl ionic media at different ionic strengths (0.1 <= I/mol L-1 <= 3.8) and temperatures (283.15 <= T/K <= 318.15). For this purpose, some literature data were used together with experimental data. In NaCl solution...

The acid–base properties of dopamine were studied in different experimental conditions by potentiometry, UV-spectrophotometry, and spectrofluorimetry. The distribution measurements between 2-methyl-1-propanol/pure water (or NaCl aqueous solutions up to I = 1.02 mol kg–1) were carried out at T = 298.15 K and 310.15 K. The potentiometric measurements...

The protonation constants and solubilities of three complexons [ethylenediamine-N,N′-disuccinic acid (EDDS), ethylene glycol bis(2-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA) and 1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid (CDTA)] are reported in aqueous solutions of NaCl with different ionic strength values (0 ≤ I ≤ 4.8 mol·L−1) and,...

Potentiometric measurements were performed in KNO3(aq), to determine the apparent protonation constants of phytate at different temperatures (278.15 <= T (K) <= 323.15) and ionic strengths (0.25 <= I (mol) dm(-3) <= 3.0) values. In general, the protonation constants decrease with increasing both temperature and ionic strength. The data reported wer...

In this paper, a potentiometric study on the thermodynamic acid base properties and solubility of three hydroxypyrones (successively indicated as maltols), namely maltol (Hma), ethylmaltol (Hema) and kojic acid (H2ka), is reported. The acid base properties of these O-donor ligands have been investigated in NaCl (0.10 ≥ I / mol L-1 ≥ 5.00), KCl (0.1...

This contribution reports the results of potentiometric and Mössbauer investigations on the formation, stability, and structure of binary and ternary mono- and binuclear complexes of Sn2+ with three hydroxocarboxylic ligands (namely L = tartrate, malate, and citrate) and chloride at T = 298.15 K in different ionic media and ionic strengths (0.15 an...

ABSTRACT: The hydrolysis of mixed-metal cations (Al3+/CH3Sn3+) was studied in aqueous solutions of NaNO3, at I = 1.00 ± 0.05 mol·dm−3 and T = 298.15 K, by potentiometric technique. Several hydrolytic mixed species are formed in this mixed system, namely, Alp(CH3Sn)q(OH)r with (p, q, r) = (1, 1, 4), (1, 1, 5), (1, 1, 6), (2, 1, 4), (1, 2, 5), (1, 4,...

The interactions between some xanthine derivatives: caffeine (Cf), theophylline (Tp), theobromine (Tb), and histamine (Hm) with phytate (Phy) were studied at T = 298.15 K and I = 0.5 mol L− 1 in aqueous NaCl solution using ISE-[H+] potentiometry. For all of the investigated systems, [(Phy)(L)Hq](q − 7) species (q = 4 to 9, depending on the maximum...

The stability of M/Phy species (M = Ag+, CH3Hg+, Mn2+, Fe2+, Co2+, VO2+, and Phy = Phytate) was determined in NaNO3, at I = 0.10 mol·dm–3 and T = 298.15 K, potentiometrically. For the VO2+/Phy system, the measurements were performed at different ionic strengths (to 0.45 mol·dm–3) and ionic media (NaNO3 and Na2SO4). In general, the formation of six...

The total solubility of three penicillin derivatives was determined, in pure water and NaCl aqueous solutions at different salt concentrations (from ∼0.15 to 1.0 mol L−1 for ampicillin and amoxicillin, and from ∼0.05 to 2.0 mol L−1 for (+)6-aminopenicillanic acid), using the shake-flask method for generating the saturated solutions, followed by pot...

An extensive study of the tin(II)/phytate (Phy) system was carried out in NaNO3(aq), at different ionic strengths (0.10 <= l/mol . L (1) <= 1.00) and temperatures (278.15 <= T/K <= 328.15), by potentiometric and voltammetric techniques. The stability and formation enthalpy changes of six SnH(q)Phy species were determined. To better characterise thi...

The speciation of mono-methylmercury(II) cation (MeHg+) in the presence of Nitrilotriacetate (NTA), Ethylenediamine-N,N,N',N'-tetraacetate (EDTA), diethylenetriamine-N,N,N',N '',N ''-pentaacetate (DTPA) and (S,S)- Ethylenediamine-N,N'-disuccinic acid (S,S-EDDS) was investigated at l = 0.1 mol (NaCl) with the aim to assess a trend of sequestering ca...

The interaction between adenosine-5′-triphosphate (ATP) and some aromatic amines (L), namely 1,2-phenylenediamine, 2-(2,4-diaminophenoxy)ethanol, 4-N-(2-hydroxyethyl)2,4-diaminoanisole, 4,5-diamino-1-N-(2-hydroxyethyl)pyrazole and 1,3-bis(2,4-diaminophenoxy) propane, was studied at T=298.15 K and I=0.06 mol⋅L−1 in NaCl aqueous solution. For all of...

This paper reports new voltammetric measurements on the interactions between tin(II) and the most important natural inorganic ligands, OH-, Cl-, F-, CO32-, SO42- and PO43-. For a better understanding of tin(II) speciation, an analysis is also given of prior data on the same systems from the literature. The formation constants were determined at t =...

The protonation constants of five structurally different aromatic amino-compounds [1,2-phenylenediamine (L1), 4-N-(2-hydroxyethyl)2,4-diaminoanisole (L2), 2-(2,4-diaminophenoxyethanol) (L3), 4-5-diamino-1-N-(2-hydroxyethyl)pyrazole (L4), 1,3-bis(2,4-diaminophenoxy)propane (L5)] obtained by potentiometric measurements in NaCl(aq) (0 mol·kg–1 ≤ I ≤ 3...

The acid–base properties of four aminophenol derivatives, namely m-aminophenol (L1), 4-amino-2-hydroxytoluene (L2), 2-amino-5-ethylphenol (L3) and 5-amino-4-chloro-o-cresol (L4), are studied by potentiometric and titration calorimetric measurements in NaCl(aq) (0 ⩽ I ⩽ 3 mol · kg−1) at T = 298.15 K. The dependence of the protonation constants on io...

Tin(II) interaction with different phosphate ligands, namely phosphate (PO4), pyrophosphate (PP), tripolyphosphate (TPP), monofluorophosphate (MFP) and adenosine-5′-triphosphate (ATP), was studied at T = 298.15 K by potentiometry and voltammetry at different ionic strengths (0.15 ≤ I/mol L− 1 ≤ 1.00) in NaNO3. We also compared our results with thos...

In this paper we report an investigation on the interactions between dioxouranium(VI) and citrate using potentiometry (H ⁺ -glass electrode) and UV-spectrophotometry. Potentiometric measurements were carried out in NaCl and KNO 3 aqueous solutions at t = 25 ºC in a wide range of experimental conditions (concentrations, ligand/metal molar ratio, pH,...

The binding capacity of five aminopolycarboxylic ligands (APCs) [nitrilotriacetate (NTA), ethylenediamine-N,N,N0, N0-tetraacetate (EDTA), (S,S)-ethylenediamine-N,N0-disuccinic acid (S,S-EDDS), diethylenetriamine-N,N,N0,N00,N00-pentaacetate (DTPA), and triethylenetetraamine-N,N,N0,N00,N000,N000-hexaacetate (TTHA)] toward the palladium(II) ion was st...